| In the present work, a gold/glass-ceramic (GP/GC) composite dental crown material and a double-layered bioceramics/Ti (hydroxyapatite-glass-ceramic/glass-ceramic/Ti, HA-GC/GC/Ti) composite implant material were investigated. The GP/GC composite has superior aesthetical stability, reliable mechanical properties and relatively cheap price, and can be used as the dental crown for the long-term restoration. HA-GC/GC/Ti composite, combined the high strength and reliability of Ti with the bio-properties of resorbable HA, provides a potential promising alternative for load-bearing implant replacement applications, such as artificial teeth or bones.The gold/glass-ceramic with non-uniform composite structure for selective strengthening and toughening from dental gold alloy particles (GP) and dental glass-ceramic (GC) was successfully fabricated by overpressing in vacuum. GPs were distributed in the highest stress region of the GP/GC composite, which is essential for the improvement of the mechanical properties and reduction of GP consumption. The detailed microstructure of the GP/GC composite was characterized and the mechanical properties of the composite were measured. The formation and function of interface between GP and GC were revealed. The strengthening and toughening mechanisms of the composite were also discussed.The double-layered bioceramics/Ti composite was fabricated from glass-ceramic (GC) powder, hydroxyapatite (HA) nano-powder and three-dimensional titanium mesh (3D Ti mesh) by dip coating & sintering process. A dense GC coating was deposited onto the 3D Ti mesh, which reduces the elastic modulus of the composite and seals off the Ti mesh. Then, a micro porous HA-GC coating was deposited on top of the dense GC coating, which is to promote the bioactivity and biocompatibility of composite. The detailed microstructure of the HA-GC/GC/Ti composite was characterized and the mechanical properties of the composite were measured. The phases of the GC/Ti interface were analyzed. The bioactivity and biocompatibility of Ti substrate, GC/Ti composite and HA-GC/GC/Ti composite were assessed subsequently.The experimental results show that:(1) The layout pattern and sequence of different GP/GC powder mixtures, the high-temperature flow properties of these mixtures during the overpressing, and the sample mold geometry were manipulated to control the distribution and location of GP for selective strengthening and toughening. The distribution of GPs are concentrated in the highest stress region of the GP/GC composite, which improves the mechanical properties of the composite, reduces the GP consumption and keeps the aesthetic property. The Vickers hardness (Hv), flexural strength (M) and fracture toughness (K1c) of the GP/GC composite are 5.45±0.4 GPa 329±28 MPa and 3.0±0.33 MPa-m1/2, respectively. Compared with the monolithic GC, the same Hv, twofold M and threefold K1c are achieved for the GP/GC composite.(2) It was observed that the matrix of the glass-ceramic is composed of leucite and feldspar. A layer of leucite was formed around each GP particle during the sintering process and AlxAuy compounds (about 20-30 nm in thickness) were produced at the GP/GC interface through chemical reactions. The chemically bonded interface has contributed significantly to the substantial improvement in GP/GC interfacial bonding. The residual compressive stresses, generated from the mismatch in CTE of GP and GC, are essential to the strengthening effect. The large scale plastic deformation of GP is essential to the toughening effect. The amorphous phases were transformed into the crystalline phases when GP/GC composites were heated at different temperatures. GP and GC further reacted in the thermal treating process and produced new compounds, such as AlmAun and AupSiq.(3) A three-dimensional Ti mesh was coated by a dense GC coating to form the 3D GC/Ti composite. The dense GC coating (about 40μm) with smooth surface consisted mainly of leucite, feldspar and some glass phases. The GC/Ti interface is composed of two reaction regions. The first region, about 10μm in thickness, is the oxygen reaction zone (Zone-I), connecting with Ti substrate, which contained TiO2 owing to the chemical reaction between Ti and O2. The second region, approximately 4μm in thickness, is the GC reaction zone (Zone-II), connecting with the GC coating, which contained TiO-2 and titanium silicide compounds (TixSiy) due to the complex chemical processes between Ti and GC. Hv of Zone-I and Zone-II are about 350-400 MPa and 450-500 MPa, respectively. The average bonding strength between dense GC coating and Ti substrate is 27 MPa. The chemical reactions between GC and Ti are essential to the bonding strength improvement. The dense GC coating is covered by the micro porous HA-GC coating, forming the HA-GC/GC/Ti composite. The HA-GC coating, with a micro-porous structure and about 120μm in thickness, is composed mainly of HA, leucite, feldspar and some glass phases. Some pores are larger than 100μm.(4) HA-GC/GC/Ti composite has the ability to induce deposition of Ca2+, PO43- and OH-ions in simulated body fluid (SBF), forming an orderly, dense and thick apatite deposition layer. Furthermore, the mouse fibroblasts (L929 cells) can attach, proliferate and grow on the composite surface. Two types of in vitro tests indicate that HA-GC/GC/Ti composite exhibits excellent osteoinduction ability, bioactivity, biocompatibility and noncytotoxicity. |
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